The crude oil refining industry is ever in need of more efficient and/or improved refining techniques to obtain products from petroleum. Many crudes, including heavy crude oil and many crudes with a high “resid” yield from distillation, are difficult to refine and have poor conversion of the heavier hydrocarbon fractions, especially asphaltenes, to valuable products. In a typical refinery process, the crude must be washed with water to remove salts and dehydrated in advance of atmospheric and vacuum distillation. Distillation recovers the lighter, valuable fractions of the oil, e.g., butane and lighter products, gasoline blending components, naphtha, kerosene, jet fuel, and distillates, e.g., diesel and heating oil. The heavier components such as medium and heavy weight gas oil may be processed in cracking and/or alkylation units to obtain LPG, gasoline, jet fuel, diesel fuel, etc., whereas the resid, representing the heaviest components such as resins and asphaltene, may be processed in a coker to obtain coke and coker gas oil and/or used as asphalt base. Some of the heavier components may conventionally contain a small amount of lube oil base stock, which are relatively low viscosity high-carbon oils, however, the conventional yields of base stocks from petroleum are quite low, typically 0.5-1 volume percent of the crude oil. Processing excessive amounts of resid such as in a delayed coker is undesirable and often not economical.
The blending optimization of crude oils has been used in refinery operations to increase the refined margins and commercial value. For example, Li et al., “Distillation Yields and Properties from Blending Crude Oils: Maxila and Cabinda Crude Oils, Maxila and Daqing Crude Oils,” Energy &Fuels (2007) 21(2), 1145-1150 (DOI: 10.1021/ef060316d), discloses the optimized blending ratio was 3:7 for Maxila and Cabinda or Daqin crude oils, and the distillation yields (<520° C.) were higher than theoretical. Demirbas et al., “Optimization of crude oil refining products to valuable fuel blends,” Petroleum Science and Technology, 35:4, 406-412, (2017) DOI: 10.1080/10916466.2016.1261162, discloses simulation software, such as linear programming modeling, to estimate and optimize the blending of crude oils, especially cheaper crude oils.
Conversion of heavy crude fractions to lighter ones often requires expensive catalysts that need recovery, regeneration, and recycle to be economic. Moreover, expensive catalysts may require pretreatment of the feedstock to ensure catalyst poisons like sulfur are removed. Conversion is generally a downstream process, often applied to the least possible quantity of material after the more valuable, easily recoverable hydrocarbon fractions have been recovered. Conversion processes often need to operate at high pressure, with the addition of external hydrogen, and/or with long residence times, to maximize conversion and minimize capital costs.
Frequently, the “upgraded” products are of poor quality and may still require blending with more valuable petroleum fractions, and even then, the blended products are often only suitable for use as fuel oil. In some instances, the heavier fractions and resid have been simply disposed of, and many places in the world are overrun with stores of such material that are difficult to economically process. The main product obtained from the resid is coke, which often has low value and entails difficult processing and handling operations. Hence, refineries have a strong incentive to minimize resid yields and coke production.
My earlier patent, U.S. Pat. No. 10,336,946 B2, discloses a process for upgrading heavy oil comprising feeding to a reactor an emulsion of 100 parts by weight heavy oil, 5-100 parts by weight water, and 1-20 parts by weight solid particulates comprising a mineral support and an oxide or acid addition salt of a Group 3-16 metal, e.g., FeCl3 on NaCl-treated clay, and spraying the feed mixture in the reactor at a high temperature and low pressure. Further improvements in liquid oil yield and quality, especially in the conversion of asphaltenes to saturates, especially isomerates, and aromatics as reflected in a SARA analysis, are desired.
As reported in Amani et al., J Pet Environ Biotechnol 2017, 8:3 DOI: 10.4172/2157-7463.1000330, in the refining of crude oil, great pains are taken in pretreating the crude to remove entrained water and salt before distillation. Sometimes the water and oil are in the form of an emulsion or rag that can be exceedingly difficult to break. Large sums are spent to dewater and desalt crude oil. Additionally, the crude oil is typically pre-heated prior to distillation, but this must be done very slowly and carefully to avoid forming coke or other deposits on the heat transfer surfaces that can result in fouling, especially in the case of heavy and/or highly viscous crudes. The industry is ever in search of ways to avoid or reduce the problems and costs incident to pretreating and preheating crude oil.
Sulfur is an undesirable crude oil contaminant. Sour crude contains more than 0.5 wt % sulfur. Crude oil stabilization can remove some H2S before refining, but organic sulfides generally build up during refining and are removed downstream with the higher-boiling constituents. There is a need in the art for better ways to remove sulfides from crude oil. An upstream pretreatment method would be especially advantageous, so that sulfur could be removed to provide a lower level of sulfur in the higher-boiling, downstream refining products.
It is known from Hancsók, Jenő et al., Importance of Isoparaffins in the Crude Oil Refining Industry, Chemical Engineering Transactions, 11, 41-47 (2007), that isomerates such as isoparaffins have the most advantageous performance properties in gasoline, diesel fuel, and base oils. However, isomerates are usually made in exacting downstream processes such as benzene saturating isomerization, catalytic hydrodewaxing of gas oils, selective isomerization of lubricating base oils, and so on. The industry would benefit from an inexpensive way to distill or otherwise process crude oil in such a manner to increase isomerate yields.
There remains a need for more efficient techniques and systems to refine and process petroleum and other hydrocarbons with ever higher yields of lighter, higher-value hydrocarbon products, while reducing the amount of resid and coke that must be handled. A solution would preferably be an upstream process to treat crude oil; minimize asphaltene and coke yields; improve saturates and/or aromatics yields; improve the quality of the saturates with increased isomerates production; improve lube oil base stock yields; minimize end product blending requirements; employ mild pressure conditions with a short residence time and high throughput using inexpensive chemical additives; reduce the need for feedstock pretreatment or conditioning to remove catalyst poisons; reduce the need for dewatering and/or desalting; facilitate crude preheating by minimizing fouling in the pre-heaters; and/or avoid adding hydrogen.